U.S. patent application number 16/114799 was filed with the patent office on 2018-12-20 for pressure vessel liner venting via nanotextured surface.
The applicant listed for this patent is Hexagon Technology AS. Invention is credited to Norman L. Newhouse.
Application Number | 20180363853 16/114799 |
Document ID | / |
Family ID | 58669011 |
Filed Date | 2018-12-20 |
United States Patent
Application |
20180363853 |
Kind Code |
A1 |
Newhouse; Norman L. |
December 20, 2018 |
PRESSURE VESSEL LINER VENTING VIA NANOTEXTURED SURFACE
Abstract
A pressure vessel has a first end with a first boss, the first
boss having a first outer surface. The vessel includes a liner
having a second outer surface, a shell disposed over the second
outer surface, and a first vent. The first vent is formed onto at
least a portion of the first outer surface and at least a portion
of the second outer surface. The first vent includes a texture that
provides a higher rate of gas flow through the first vent than
through a portion of an interface of the liner and shell lacking
the texture. In another aspect, a pressure vessel has a first end
and a second end, a plurality of first longitudinal vents and a
plurality of second longitudinal vents. At least one of first
longitudinal vents is circumferentially offset around the pressure
vessel from at least one of the second longitudinal vents.
Inventors: |
Newhouse; Norman L.;
(Lincoln, NE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hexagon Technology AS |
Alesund |
|
NO |
|
|
Family ID: |
58669011 |
Appl. No.: |
16/114799 |
Filed: |
August 28, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15485483 |
Apr 12, 2017 |
10088110 |
|
|
16114799 |
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62337450 |
May 17, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F17C 13/002 20130101;
F17C 2205/0305 20130101; F17C 1/06 20130101; F17C 2203/0621
20130101; F17C 2223/0123 20130101; C09K 13/00 20130101; F17C
2203/067 20130101; B82Y 40/00 20130101; F17C 2201/056 20130101;
F17C 2260/011 20130101; F17C 2203/0636 20130101; F17C 1/16
20130101; F17C 2260/038 20130101; F17C 2260/037 20130101; F17C
2221/033 20130101; F17C 2201/0109 20130101; F17C 2203/0619
20130101; F17C 2203/066 20130101; F17C 2209/2154 20130101; F17C
2203/0604 20130101; C23F 4/04 20130101; F17C 2223/033 20130101;
F17C 2221/011 20130101; Y02E 60/32 20130101; F17C 2221/014
20130101; F17C 2203/0663 20130101; F17C 2223/035 20130101; F17C
2221/012 20130101; F17C 2223/0153 20130101; Y02E 60/321 20130101;
C23F 1/00 20130101; F17C 2221/035 20130101 |
International
Class: |
F17C 13/00 20060101
F17C013/00; F17C 1/16 20060101 F17C001/16; F17C 1/06 20060101
F17C001/06 |
Claims
1-20. (canceled)
21. A pressure vessel including: a liner having an outer surface; a
shell disposed over the outer surface; and a vent formed onto at
least a portion of the outer surface, the vent including a texture
that provides a higher rate of gas flow through the vent than
through a portion of an interface of the liner and shell lacking
the texture.
22. The pressure vessel of claim 21 wherein the vent includes a
nanotextured portion of the outer surface.
23. The pressure vessel of claim 21 wherein the vent is
elongated.
24. The pressure vessel of claim 23 wherein the vent is aligned
substantially parallel to a longitudinal axis of the pressure
vessel.
25. The pressure vessel of claim 21 wherein the pressure vessel has
a cylindrical portion, and wherein the vent extends at least from
the cylindrical portion to an end of the pressure vessel.
26. The pressure vessel of claim 25 wherein the vent extends at
least to a longitudinal midpoint of the pressure vessel.
27. The pressure vessel of claim 21 wherein an end of the vent is
disposed on a neck of a boss.
28. The pressure vessel of claim 21 wherein an end of the vent is
open to the atmosphere.
29. The pressure vessel of claim 21 wherein the texture includes a
plurality of peaks and valleys, and wherein a distance between
adjacent peaks is in a range between about 5 micrometers and about
20 micrometers.
30. A pressure vessel having a first end and a second end, the
vessel including: a liner having an outer surface; a shell disposed
over the outer surface; a first longitudinal vent formed onto a
first portion of the outer surface and including a texture that
provides a higher rate of gas flow through the first longitudinal
vent than through a portion of an interface of the liner and shell
lacking the texture; and a second longitudinal vent formed onto a
second portion of the outer surface and including the texture,
which provides a higher rate of gas flow through the second
longitudinal vent than through a portion of the interface lacking
the texture; wherein the first longitudinal vent is
circumferentially offset around the pressure vessel from the second
longitudinal vent.
31. The pressure vessel of claim 30 wherein at least one of the
longitudinal vents is aligned substantially parallel to a
longitudinal axis of the pressure vessel.
32. The pressure vessel of claim 30 wherein at least one of the
first and second longitudinal vents includes a nanotextured portion
on a boss.
33. The pressure vessel of claim 30 wherein the pressure vessel has
a cylindrical portion, and wherein at least one of the first or
second longitudinal vents extends at least from the cylindrical
portion to a boss.
34. The pressure vessel of claim 30 wherein an end of at least one
of the first or second longitudinal vents is disposed on a neck of
a boss.
35. The pressure vessel of claim 30 wherein an end of at least one
of the first or second longitudinal vents is open to the
atmosphere.
36. The pressure vessel of claim 30 wherein at least one of the
longitudinal vents extends at least to a longitudinal midpoint of
the pressure vessel.
37. The pressure vessel of claim 30 wherein the texture includes a
plurality of peaks and valleys, and wherein a distance between
adjacent peaks is in a range between about 5 micrometers and about
20 micrometers.
38. A method for forming a pressure vessel including: forming a
liner having an outer surface; imparting a texture on a portion of
the outer surface to form a vent; and forming a shell over the
outer surface; wherein the vent is configured to allow a higher
rate of gas flow therethrough than through a portion of an
interface of the liner and shell lacking the texture.
39. The method of claim 38, wherein imparting the texture includes
laser etching.
40. The method of claim 38, wherein imparting the texture includes
chemical etching.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of priority from U.S.
Provisional Patent Application No. 62/337,450, filed May 17, 2016,
entitled "Pressure Vessel Liner Venting via Nanotextured Surface,"
which is hereby incorporated by reference in its entirety.
BACKGROUND
[0002] Pressure vessels are commonly used for containing a variety
of fluids under pressure, such as storing hydrogen, oxygen, natural
gas, nitrogen, propane, methane, and other fuels, for example.
Suitable container shell materials include laminated layers of
wound fiberglass filaments or other synthetic filaments bonded
together by a thermal-setting or thermoplastic resin. A polymeric
or other non-metallic resilient liner or bladder often is disposed
within the composite shell to seal the vessel and prevent internal
fluids from contacting the composite material. The composite
construction of the vessels provides numerous advantages such as
lightness in weight and resistance to corrosion, fatigue and
catastrophic failure. These attributes are due at least in part to
the high specific strengths of the reinforcing fibers or filaments
that are typically oriented in the direction of the principal
forces in the construction of the pressure vessels.
[0003] FIGS. 1 and 2 illustrate a conventional elongated pressure
vessel 10, such as that disclosed in U.S. Pat. No. 5,476,189,
entitled "Pressure vessel with damage mitigating system," which is
hereby incorporated by reference. Vessel 10 has a main body section
18 with end sections 14. A boss 16, typically constructed of
aluminum, is provided at one or both ends of the vessel 10 to
provide a port for communicating with the interior of the vessel
10. The vessel 10 has an inner polymer liner 20 covered by an outer
composite shell 12. In this case, "composite" means a fiber
reinforced resin matrix material, such as a filament wound or
laminated structure. The composite shell 12 resolves structural
loads on the vessel 10.
[0004] Although the liner 20 provides a gas barrier under typical
operating conditions, the design of a pressure vessel 10 of this
type produces a phenomenon wherein gas diffuses into the liner 20
under pressurization. When depressurization of the vessel 10
occurs, this gas diffuses into the interface or space between the
liner 20 and the composite shell 12. A pocket of gas may thereby be
formed, causing the liner 20 to bulge inward. At low pressure,
laminate strain in the composite shell 12 is low, and microcracks
in the shell 18 close up, effectively forming a seal; when a higher
pressure is reached, those microcracks open up again, thereby
allowing expulsion of the trapped pocket of gas. Thus, when the
vessel 10 is re-pressurized, pressure builds up against liner 20,
pushing against the trapped gas pocket, making the bulge in the
liner 20 smaller until the gas is ultimately expelled through the
composite shell 12 to the atmosphere. Such expulsion of gas through
shell 12 may occur in a short time interval and can cause a
significant concentration of gas to become present in the
surroundings of the vessel 10. This may set off a leak detector
around the vessel 10, when actually there is no steady leak from
the liner 20.
SUMMARY
[0005] In one aspect, a pressure vessel has a first end with a
first boss, the first boss having a first outer surface. The vessel
includes a liner having a second outer surface, a shell disposed
over the second outer surface, and a first vent. The first vent is
etched onto at least a portion of the first outer surface and at
least a portion of the second outer surface. The first vent
includes a texture that provides a higher rate of gas flow through
the first vent than through a portion of an interface of the liner
and shell lacking the texture.
[0006] In another aspect, a pressure vessel has a first end and a
second end. The first end has a first boss having a first outer
surface, and the second end has a second boss having a second outer
surface. The vessel includes a liner having a third outer surface,
a shell disposed over the third outer surface, a plurality of first
longitudinal vents and a plurality of second longitudinal vents.
Each of the first longitudinal vents is etched onto a portion of
the first outer surface and a portion of the third outer surface.
Each of the first longitudinal vents includes a texture that
provides a higher rate of gas flow through the first longitudinal
vent than through a portion of an interface of the liner and shell
lacking the texture. Each of the second longitudinal vents is
etched onto a portion of the second outer surface and a portion of
the third outer surface. Each of the second longitudinal vents
includes a texture that provides a higher rate of gas flow through
the second longitudinal vent than through a portion of an interface
lacking the texture. At least one of first longitudinal vents is
circumferentially offset around the pressure vessel from at least
one of the second longitudinal vents.
[0007] This disclosure, in its various combinations, either in
apparatus or method form, may also be characterized by the
following listing of items: [0008] 1. A pressure vessel having a
first end with a first boss, the first boss having a first outer
surface, and the vessel including: [0009] a liner having a second
outer surface; [0010] a shell disposed over the second outer
surface; and [0011] a first vent formed onto at least a portion of
the first outer surface and at least a portion of the second outer
surface, the first vent including a texture that provides a higher
rate of gas flow through the first vent than through a portion of
an interface of the liner and shell lacking the texture. [0012] 2.
The pressure vessel of item 1 wherein the first vent includes a
nanotextured portion of the first outer surface and wherein the
first vent includes a nanotextured portion of the second outer
surface. [0013] 3. The pressure vessel of any of items 1-2 wherein
the first vent is elongated. [0014] 4. The pressure vessel of item
3 wherein the first vent is aligned substantially parallel to a
longitudinal axis of the pressure vessel. [0015] 5. The pressure
vessel of any of items 1-4 wherein the pressure vessel has a
cylindrical portion, and wherein the first vent extends at least
from the cylindrical portion to the first boss. [0016] 6. The
pressure vessel of item 5 wherein the first vent extends at least
to a longitudinal midpoint of the pressure vessel. [0017] 7. The
pressure vessel of any of items 1-6 wherein an end of the first
vent is disposed on a neck of the first boss. [0018] 8. The
pressure vessel of item 7 wherein the end is open to the
atmosphere. [0019] 9. The pressure vessel of any of items 1-8
wherein the textures includes a plurality of peaks and valleys, and
wherein a distance between adjacent peaks is preferably in a range
between about 5 micrometers and about 20 micrometers, but the
distance between adjacent peaks may longer or shorter. [0020] 10. A
pressure vessel having a first end with a first boss having a first
outer surface, the pressure vessel having a second end with a
second boss having a second outer surface, the vessel including:
[0021] a liner having a third outer surface; [0022] a shell
disposed over the third outer surface; [0023] a plurality of first
longitudinal vents, each of the first longitudinal vents formed
onto a portion of the first outer surface and a portion of the
third outer surface, each first longitudinal vent including a
texture that provides a higher rate of gas flow through the first
longitudinal vent than through a portion of an interface of the
liner and shell lacking the texture; and [0024] a plurality of
second longitudinal vents, each of the second longitudinal vents
formed onto a portion of the second outer surface and a portion of
the third surface, each second longitudinal vent including the
texture, which provides a higher rate of gas flow through the
second longitudinal vent than through a portion of the interface
lacking the texture; [0025] wherein at least one of first
longitudinal vents is circumferentially offset around the pressure
vessel from at least one of the second longitudinal vents. [0026]
11. The pressure vessel of item 10 wherein at least one of the
longitudinal vents is aligned substantially parallel to a
longitudinal axis of the pressure vessel. [0027] 12. The pressure
vessel of any of items 10-11 wherein at least one of the first and
second longitudinal vents includes a nanotextured portion of the
third outer surface. [0028] 13. The pressure vessel of any of items
10-12 wherein the pressure vessel has a cylindrical portion, and
wherein at least one of the first longitudinal vents extends at
least from the cylindrical portion to the first boss. [0029] 14.
The pressure vessel of any of items 10-13 wherein an end of at
least one of the first longitudinal vents is disposed on a neck of
the first boss. [0030] 15. The pressure vessel of item 14 wherein
the end is open to the atmosphere. [0031] 16. The pressure vessel
of any of items 10-15 wherein at least one of the longitudinal
vents extends at least to a longitudinal midpoint of the pressure
vessel. [0032] 17. The pressure vessel of any of items 10-16
wherein the textures includes a plurality of peaks and valleys, and
wherein a distance between adjacent peaks is preferably in a range
between about 5 micrometers and about 20 micrometers, but the
distance between adjacent peaks may longer or shorter. [0033] 18. A
method for forming a pressure vessel including: [0034] providing a
boss having a first outer surface; [0035] forming a liner in
contact with the boss, the liner having a second outer surface; and
[0036] forming a vent on the boss and liner by imparting a
nanotexture on at least a portion of the first outer surface and at
least a portion of the second outer surface. [0037] 19. The method
of item 18, wherein imparting the nanotexture includes laser
etching. [0038] 20. The method of any of items 18-19, wherein
imparting the nanotexture includes chemical etching.
[0039] This summary is provided to introduce concepts in simplified
form that are further described below in the Detailed Description.
This summary is not intended to identify key features or essential
features of the disclosed or claimed subject matter and is not
intended to describe each disclosed embodiment or every
implementation of the disclosed or claimed subject matter.
Specifically, features disclosed herein with respect to one
embodiment may be equally applicable to another. Further, this
summary is not intended to be used as an aid in determining the
scope of the claimed subject matter. Many other novel advantages,
features, and relationships will become apparent as this
description proceeds. The figures and the description that follow
more particularly exemplify illustrative embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] The disclosed subject matter will be further explained with
reference to the attached figures, wherein like and analogous
structure or system elements are referred to by like reference
numerals throughout the several views. All descriptions of
structures apply equally to like or analogous structures.
[0041] FIG. 1 is a side elevation view of a typical elongated
pressure vessel.
[0042] FIG. 2 is a partial cross-sectional view through one end of
such a pressure vessel, taken along line 2-2 of FIG. 1.
[0043] FIG. 3 is an enlarged partial cross-sectional view of a
pressure vessel incorporating an exemplary embodiment of a
nano-textured liner surface vent of the present disclosure.
[0044] FIG. 4 is a partial cross-sectional view, taken along line
4-4 of FIG. 3, of a first exemplary longitudinal nano-textured
liner surface vent at the interface of the liner and composite
shell.
[0045] FIG. 5 is a side elevation view of an elongated pressure
vessel incorporating exemplary arrangements of longitudinal
nano-textured liner surface vents.
[0046] FIGS. 6(a)-6(i) are photographs showing topographical
features of exemplary nano-textured liner surface vents.
[0047] While the above-identified figures set forth one or more
embodiments of the disclosed subject matter, other embodiments are
also contemplated, as noted in the disclosure. In all cases, this
disclosure presents the disclosed subject matter by way of
representation and not limitation. It should be understood that
numerous other modifications and embodiments can be devised by
those skilled in the art which fall within the scope of the
principles of this disclosure.
[0048] The figures may not be drawn to scale. In particular, some
feature may be enlarged relative to other features for clarity.
Moreover, where terms such as above, below, over, under, top,
bottom, side, right, left, etc., are used, it is to be understood
that they are used only for ease of understanding the description.
It is contemplated that structures may be otherwise oriented.
DETAILED DESCRIPTION
[0049] This disclosure relates to providing a vent path to prevent
gas and pressure build up between the liner 20' and the composite
shell 12 of a pressure vessel 10'. This vent path allows gas, such
as hydrogen, to escape at a steadier rate, preventing leak detector
disturbances. Moreover, the disclosed vent path prevents the liner
20' from bulging or buckling inwardly, thereby preventing localized
weakening that may result in shorter life of the liner 20'.
Exemplary embodiments of such a vent path are provided as
longitudinal vents 22 of FIGS. 3-5. As shown in FIG. 3, an end 22a
of longitudinal vent 22 adjacent boss 16 is open to the
atmosphere.
[0050] A method of forming a pressure vessel 10' includes mounting
a boss 16 on a mandrel (not shown) and allowing a fluid polymer
material for liner 20' to flow around flange 32 and into grooves 34
of boss 16. The liner material then solidifies, thereby forming
liner 20', which is mechanically interlocked with boss 16.
Accordingly, even under extreme pressure conditions, separation of
liner 20' from boss 16 is prevented.
[0051] In some embodiments, the liner 20' can be made of plastic,
elastomers, or other polymers, and can be manufactured by
compression molding, blow molding, injection molding or any other
generally known technique. In other embodiments, the liner 20' can
include other materials, including but not limited to metals such
as steel, aluminum, nickel, titanium, stainless steel, and any
alloys thereof. Suitable metals can be generally characterized as
having a high modulus of elasticity. In one embodiment, the liner
20' is formed of blow molded high density polyethylene (HDPE).
[0052] Referring to FIGS. 3 and 4, in forming vessel 10', prior to
winding fibers of composite material around liner 20' to form shell
12, one or more vents 22 are etched onto at least a portion of
outer surface 24 of the liner 20' and at least a portion of the
outer surface of boss 16'. The etching provides a vent 22 having a
rough surface texture at the liner and shell interface 26, wherein
the texture provides a higher rate of gas flow through the vent 22
than through a portion of interface 26 lacking the texture. Vent 22
thereby providing a tortuous pathway along the roughened surface 24
of liner 20' for gas to escape from interface 26 between liner 20'
and shell 12. An optional auxiliary outer layer may also be formed
on shell 12.
[0053] As shown in FIG. 5, in an exemplary embodiment, each vent 22
extends from a boss 16' at least to center 30 of pressure vessel
10'. In an embodiment, a vent 22 may extend from a first boss 16a'
all the way to a second boss 16b'. In still other embodiments, an
etched vent surface may be provided substantially over an entire
surface 24 of liner 20' facing shell 12, rather than along
longitudinal pathways. As shown in FIG. 3, in an exemplary
embodiment, an end of vent 22a is exposed to the atmosphere outside
of pressure vessel 10'. The vent 22 defines a tortuous path on the
etched surface portion of surface 24, through which fluid at the
interface 26 between shell 12 and the underlying liner 20' and boss
16' can travel to exhaust at vent end 22a to the atmosphere. Vent
22 is formed by laser, chemical, or mechanical etching, for
example, to modify at least portions of the outer surface 24 of the
liner 20' and the outer surface of the boss 16'. In an exemplary
embodiment, about three to about four laser etched vents 22 are
provided for a pressure vessel 10'. However, the use of more or
fewer vents 22 on a pressure vessel is also contemplated.
[0054] Outer shell 12 is formed surrounding the liner 20' and at
least a portion of flange 32 of boss 16'. Suitable materials for
shell 12 include a composite of laminated layers of wound
fiberglass fibers or filaments or other synthetic filaments bonded
together by a thermal-setting or thermoplastic resin. The fiber may
be fiberglass, aramid, carbon, graphite, or any other generally
known fibrous reinforcing material or combination of fibrous
reinforcing materials. The resin matrix used may be epoxy,
polyester, vinyl ester, thermoplastic or any other suitable
resinous material capable of providing fiber to fiber bonding,
fiber layer to layer bonding, and the fragmentation resistance
required for the particular application in which the vessel is to
be used. In an exemplary method, a dispensing head for the fibers
moves in such a way as to wrap the fiber on the liner 20' in a
desired pattern. If the vessel 10' is cylindrical, rather than
spherical, fiber winding is normally applied in both a
substantially longitudinal (helical) and a circumferential (hoop)
wrap. This winding process is defined by a number of factors, such
as resin content, fiber configuration, winding tension, and the
pattern of the wrap in relation to the axis of the liner 20'.
Details relevant to the formation of an exemplary pressure vessel
are disclosed in U.S. Pat. No. 4,838,971, entitled "Filament
Winding Process and Apparatus," which is incorporated herein by
reference.
[0055] When fluid is contained in vessel 10' under pressure, some
fluid may permeate through liner 20' and into the interface 26
between liner 20' and shell 12. The presence of gas at the
interface 26 may compromise the sealed relationship of the boss 16
and liner 20', cause localized weakening of liner 20', and cause
gas expulsion through shell 12 to the atmosphere outside vessel
10'. In an exemplary embodiment, a single or plurality of vents 22
are provided on exterior surface 24 of liner 20' to fluidly connect
the interface 26 to the atmosphere via a designated pathway defined
by the portion of surface 24 that is provided with a nanotexture,
such as by etching.
[0056] In an exemplary embodiment, as illustrated by FIG. 5,
longitudinal vents 22 extend from at least a boss 16a' or 16b' to a
point near or past center 30 of the cylindrical main section 18 of
the cylindrical vessel 10'. The center 30 of the cylindrical main
body section 18 is typically the most compliant (i.e., same
strength; but less edge support) portion of the vessel 10' and is
thus the most likely area to exhibit bulging or buckling of the
vessel liner 20 inwardly because of gas buildup. In an exemplary
embodiment, at least one of the longitudinal vents 22 from boss 16a
and at least one of the longitudinal vents 22 from boss 16b extends
to and/or beyond the intermediate portion of the pressure vessel
10' proximate center 30. Thus, an arrangement of vents 22 as shown
in FIG. 5 places about twice the number of vents 22 proximate
center 30 compared to the number of vents proximate end sections
14a', 14b'.
[0057] On any particular vessel, only one longitudinal vent 22 may
be required, such as shown in the left half of FIG. 5. Multiple
longitudinal vents 22 may also be provided, however, such as shown
in the right half of FIG. 5. In one exemplary embodiment, vents 22
are arranged so that circumferentially adjacent vents extend to
opposite bosses 16a', 16b'. In such a case, a first plurality of
longitudinal vents 22 are directed to the boss 16a' on one end 14a'
of vessel 10' and a second plurality of longitudinal vents 22 are
directed to the boss 16b' on the opposite end 14b' of vessel 10'.
The two sets of longitudinal vents 22 are alternately arranged
around the circumference of vessel 10' so that they extend
alternately from the respective boss 16a', 16b' at least to center
line 30. In the illustrated embodiment, two circumferentially
adjacent longitudinal vents 22 are circumferentially offset from
each other and are directed to opposite ends 14a', 14b' of vessel
10'. In yet another embodiment, a single longitudinal vent extends
from one boss 16a ' to the opposite boss 16b'. In the illustrated
embodiment, pressure vessel 10' has an intermediate, substantially
cylindrical portion proximate center 10.
[0058] In an exemplary embodiment, a vessel 10' having a length of
about 24 inches to about 60 inches includes about four vents 22
having a width of about 1/4 inch to about 1/2 inch each. However,
it is contemplated that more or fewer, wider or narrower, vents 22
could be used on any vessel. While the illustrated embodiments show
one or a plurality of discrete longitudinal vents 22, it is also
contemplated that a more extensive venting layer may be used,
wherein more of surface 24 liner 20` is provided with a
nanotextured characteristic. Moreover, while vents 22 are
illustrated as including straight lines, it is contemplated that
the vents 22 may alternatively or additionally include a serpentine
or other shape or configuration. It is contemplated that fewer or
more vents 22 may be used on a pressure vessel 10'. Moreover, the
vents 22 may be sized differently than in the exemplary
embodiments. Additionally, while a plurality of vents 22 for a
particular pressure vessel 10' may all be of the same size and
shape and symmetrically placed about a circumference of pressure
vessel 10', it is also contemplated that vents 22 may alternatively
possess a combination of different sizes, shapes, changing widths,
and placements in a single pressure vessel.
[0059] FIGS. 6(a)-6(i) are photographs showing topographical
features of exemplary nano-textured vents 22. As shown in FIG. 3, a
texturing or etching process is completed on the outer surface 24
of liner 20' and the outer surface of flange 32 and neck 28 of boss
16 to form vents 22. Such a texturing or etching process may be
accomplished with sandblasting, knurling, laser light, chemicals,
nano-silica particle blasting, or other means of imparting surface
deformities to outer surface 24 of liner 20'. While etching
processes generally remove material from a surface, other suitable
ways of imparting surface deformities to outer surface 24 of liner
20' including depositing material on outer surface 24 of liner 20'
to form a textured surface capable of providing a higher gas flow
rate thereon compared to an adjacent surface without material
deposited thereon. The resulting surface of vent 22, embodiments of
which are shown in FIGS. 6(a)-6(i), includes a plurality of surface
peaks (some of which are labeled with reference numbers 1 and 2)
and valleys between the peaks. A 5 micrometer length gauge is shown
in FIGS. 6(a)-6(i). In an exemplary embodiment, each vent 22 has a
surface texture in which a distance between adjacent surface peaks
averages between about 5 micrometers and about 20 micrometers.
Because of the small scale of the textured surface, it is sometimes
referred to as a "nanotextured surface." The "nanotextured surface"
is to be distinguished from surfaces having macro-scale features
such as machined channels and grooves. In an exemplary embodiment,
the surface texture of vents 22 is fine enough that liquids such as
the matrix (e.g., resin and filament) material for shell 12 does
not fully penetrate or wet the surface, but rather floats on the
peaks, thereby allowing a porous gas vent path 22 to remain within
the valleys of the nanotextured portion of surface 24.
[0060] An exemplary, non-limiting embodiment of a pressure vessel
10' is described and shown. In an exemplary embodiment, such as
illustrated in FIGS. 3-5, pressure vessel 10' has a first end 14a'
with a first boss 16a', the first boss 16a' having a first outer
surface 38. Liner 20' has a second outer surface 24. A composite
shell 12 is disposed over the second outer surface 24. A first vent
22 is etched onto at least a portion of the first outer surface 38
and at least a portion of the second outer surface 24, the first
vent 22 including a texture that provides a higher rate of gas flow
through the first vent 22 than through a portion of an interface 26
of the liner 20' and shell 12 lacking the texture.
[0061] In an exemplary embodiment, the first vent 22 includes a
nanotextured portion of the first outer surface 38 and a
nanotextured portion of the second outer surface 24. In an
exemplary embodiment, the first vent 22 is elongated. In an
exemplary embodiment, the first vent 22 is aligned substantially
parallel to a longitudinal axis 36 of the pressure vessel 10'. In
an exemplary embodiment, the pressure vessel 10' has a cylindrical
portion 18, and the first vent 22 extends at least from the
cylindrical portion 18 to the first boss 16a'. In an exemplary
embodiment, the first vent 22 extends at least to a longitudinal
midpoint 30 of the pressure vessel 10'. In an exemplary embodiment,
an end 22a of the first vent 22 is disposed on a neck 28 of the
first boss 16a'. In an exemplary embodiment, the end 22a is open to
the atmosphere. In an exemplary embodiment, the textures includes a
plurality of peaks and valleys, and a distance between adjacent
peaks is in a range between about 5 micrometers and about 20
micrometers, as illustrated in FIGS. 6(a)-6(i).
[0062] In an exemplary embodiment, a pressure vessel 10' has a
first end 14a' with a first boss 16a' having a first outer surface
38 and a second end 14b' with a second boss a16b' having a second
outer surface 38. A liner 20' has a third outer surface 24. A shell
12 is disposed over the third outer surface 24. A plurality of
first longitudinal vents 22 is etched onto a portion of the first
outer surface 38 and a portion of the third outer surface 24, each
first longitudinal vent 22 including a texture that provides a
higher rate of gas flow through the first longitudinal vent 22 than
through a portion of an interface 26 of the liner 20' and shell 12
lacking the texture. A plurality of second longitudinal vents 22 is
etched onto a portion of the second outer surface 38 and a portion
of the third outer surface 24, each second longitudinal vent 22
including a texture that provides a higher rate of gas flow through
the second longitudinal vent 22 than through a portion of an
interface 26 of the liner 20' and shell 12 lacking the texture. In
an exemplary embodiment, at least one of first longitudinal vents
22 is circumferentially offset around the pressure vessel 10' from
at least one of the second longitudinal vents 22. In an exemplary
embodiment, at least one of the longitudinal vents 22 is aligned
substantially parallel to a longitudinal axis 36 of the pressure
vessel 10'. In an exemplary embodiment, at least one of the first
and second longitudinal vents 22 includes a nanotextured portion of
the third outer surface 24.
[0063] In an exemplary embodiment, the pressure vessel 10' has a
cylindrical portion 18, and at least one of the first longitudinal
vents 22 extends at least from the cylindrical portion 18 to the
first boss 16a'. In an exemplary embodiment, an end 22a of at least
one of the first longitudinal vents 22 is disposed on a neck 28 of
the first boss 16'. In an exemplary embodiment, the end 22a is open
to the atmosphere. In an exemplary embodiment, at least one of the
longitudinal vents 22 extends at least to a longitudinal midpoint
30 of the pressure vessel 10'. In an exemplary embodiment, the
textures includes a plurality of peaks and valleys, and a distance
between adjacent peaks is in a range between about 5 micrometers
and about 20 micrometers, as illustrated in FIGS. 6(a)-6(i).
[0064] In an exemplary embodiment, a method for forming a pressure
vessel 10' includes providing a boss 16' having a first outer
surface 38; forming a liner 20' in contact with the boss 16', the
liner 20' having a second outer surface 24; and forming a vent 22
on the boss 16' and liner 20' by imparting a nanotexture on at
least a portion of the first outer surface 38 and at least a
portion of the second outer surface 24. In an exemplary embodiment,
imparting the nanotexture includes laser etching. In an exemplary
embodiment, imparting the nanotexture includes chemical
etching.
[0065] Although the subject of this disclosure has been described
with reference to several embodiments, workers skilled in the art
will recognize that changes may be made in form and detail without
departing from the scope of the disclosure. In addition, any
feature disclosed with respect to one embodiment may be
incorporated in another embodiment, and vice-versa.
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